1. Field of the Invention
The present invention relates to a dielectric-line integrated circuit formed by a combination of dielectric-line components, each having a dielectric strip between two electrically conductive flat-plates located substantially parallel to each other.
2. Description of the Related Art
An application of the above type of dielectric-line integrated circuit, for example, is a vehicle-mounted millimeter-wave radar using dielectric lines, which is formed by a combination of various types of dielectric-line components, such as an oscillator, a circulator, and a mixer.
Two examples of conventional vehicle-mounted millimeter-wave radar are shown in FIGS. 14 and 15. In FIG. 14, the radar includes electrically conductive flat-plates 1a and 2a, which also serve as the radar body, i.e., a casing for dielectric-line components. Hollows indicated by H1, H2 and H3 are formed on the opposing surfaces of the conductive plates 1a and 2a. Reference numerals 10 and 11 respectively indicate an oscillator and a circulator which are respectively fit into the hollows H1 and H2. A mixer (not shown) is fit into the hollow H3. Disposed between the conductive plates 1a and 2a are dielectric strips 6, 7 and 8 and terminating devices 9 and 12. With this arrangement, in operation, an oscillation signal output from the oscillator 10 passes through one port of the circulator 11 and the dielectric strip 6, and radiates from a horn 13 to the exterior. Conversely, electromagnetic waves propagating via the dielectric strip 6 in the direction opposite to the transmitting direction of the oscillation signal do not return to the oscillator 10 but are transmitted to the terminating device 12 connected to another port of the circulator 11. Waves reflected from a subject are received by a horn 14 and input into the mixer via the dielectric strip 8. A coupler is interposed between the dielectric strips 6 and 7 and between the dielectric strips 7 and 8, whereby reflection signal indicating the waves reflected from the subject and a local signal are both input into the mixer.
In another example of the dielectric-line integrated circuit shown in FIG. 15, apertures A1, A2 and A3 are formed on the upper conductive plate 2a, so that the oscillator 10, the circulator 11, and a mixer (unillustrated) can be respectively fit into the apertures A1, A2 and A3 from the exterior in the state in which the two conductive plates 1a and 2a are assembled. The other details of this example are similar to the example illustrated in FIG. 14.
In the dielectric-line integrated circuits shown in FIGS. 14 and 15, the characteristics of the individual dielectric-line components, such as an oscillator and a circulator, can be singly measured and calibrated, and then, the dielectric-line components can be attached to the radar body (i.e., the conductive plates), thereby constructing a single dielectric-line integrated circuit. This type of integrated circuit is more advantageous over a dielectric-line integrated circuit of the type in which all of the dielectric lines are formed between two conductive plates, because the evaluation and adjustment of the overall characteristics can be made simple, and the individual dielectric-line components can be formed into modules.
However, the following problem is encountered in aligning the dielectric strips formed in a plurality of dielectric-line components when the components are assembled and integrated into a single circuit. More specifically, referring to FIG. 14, the dimensions of the dielectric-line components are determined so that the heights of the two dielectric strips can be equal to each other in the state in which the bottom surface of the component is placed on the bottom surface of the hollow formed in the dielectric-line body. The dimensional precision of the respective components should be extremely high, in order to avoid changing the characteristics of the components due to a displacement of the dielectric strips.
Moreover, in known dielectric-line components, for example, in a circulator, upper and lower dielectric plates 2b and 1b are configured, as illustrated in FIG. 16, to match the end faces of three-port dielectric strips, thereby inevitably forming the overall circulator generally in a regular triangle shape, and forming the mating hollows and apertures of the dielectric-line body in the same shape as well. However, conductive plates having such flat end faces or having hollows and apertures with internal flat surfaces are difficult to fabricate and also occupy a large area of a resulting dielectric-line integrated circuit. In contrast, the end faces of dielectric strips are desirably flat to be easily manufactured. Thus, for example, if the shape of a dielectric strip 3b remains unchanged (i.e., flat), and the upper and lower conductive plates 1b and 2b are formed in a disc-like shape, the following inconveniences are generated. If the end face of the dielectric strip 3b disposed in the circulator is located not to project from the end face of the conductive plate, as illustrated in FIG. 17A, a clearance is disadvantageously formed between the end face of the dielectric strip 3b and the end face of a mating dielectric strip 3a. Conversely, if the end face of the dielectric strip 3b formed in the circulator projects to reach the end face of the mating dielectric strip 3a, as shown in FIG. 17B, the dielectric-line component having the dielectric strip 3b is too tight to fit into the aperture A2 shown in FIG. 15, since the edge of the strip 3b tightly hits the internal surface of the aperture A2. Or, the component having the dielectric strip 3b is forced into the aperture A2, resulting in damaging the edge of the dielectric strip 3b.